Soil aggregate stability is a key property of soil,and reflects soil fertility.Soil aggregate stability index(ASI) was formed through the transition matrix between dry sieving results and Yoder method results,and conserving-probability of each size aggregate on the basis of 3 reasonable assumptions.The ASI is identical to the result by references,which shows that the transition matrix can be used to evaluate the soil aggregate stability.The transition matrix was then used to analyse anti-break ability of different size aggregates.Results show that there are difference effects for each size aggregate with 4 methods of simulation rainfall,wetting-drying cycles one time,wetting-drying cycles ten time,and Yoder wet sieving.There is a good linear relationship between content of more than 0.25 mm water stable aggregate and ASI in a total tendency,but not all size aggregate stability heightenes with 0.25 mm water stable aggregate content increasing.The transition method utilizes all information of aggregate analysis,and can be a better tool to understand soil aggregate.